Tribocorrosion of total hip replacements

The performance of metal-on-metal total hip replacements is largely determined by their propensity to degrade in vivo. Degradation occurs through the complex interactions between wear and corrosion (termed tribocorrosion) and leads to the production of metallic particulate debris and metallic ions. The interaction of these degradation products with the body can lead to serious health complications, within patients, and is an important factor in determining the success of prostheses. Testing was undertaken on a reciprocating pin-on-plate tribometer and a single station hip joint simulator. Each test rig was instrumented, with a 3-electrode electrochemical cell, to enable in-situ corrosion monitoring during tribological testing. Testing was focused around 36mm metal-on-metal bearing surfaces in both saline and bovine serum solutions but consideration was also given to metal-on-polymer interfaces. Corrosion was found to contribute substantially to material degradation within metal-on-metal contacts, both in the tribometer and in the hip simulator. Within metal-on-polymer interfaces, the material degradation, due to corrosion, was negligible when compared with metal-on-metal surfaces. In-situ corrosion measurements were influenced by the variance in tribological conditions of the bearing. These unique findings enabled, for the first time, observations of both the corrosion and tribological performance of the bearing to be assessed in real-time.